It is an unfortunate fact that terrorists often attempt to influence the course of political events through the use of violence. One infamous means of implementing these violent actions is by strategically placing bombs wherein they will cause the greatest devastation and have the greatest political impact, such as by placing bombs in mailboxes or trash containers in densely populated areas. Likewise, land mines are placed in areas of traffic so that the victims will be affected when the vehicle traverses the mine. Indeed, bombs seem almost to be a weapon of choice for terrorists. As is well known, terrorist targets are typically chosen on the basis of their vulnerability to such attack and are frequently, if not purposefully, selected without regard for human life.
Crowds of people can, therefore, be an attractive terrorist target due to the intense public reaction that mass murder evokes. Containers located in crowded areas, such as mailboxes and trash containers, are also attractive targets for terrorists.
Because mailboxes and trash containers are so ubiquitous in densely populated areas, it is nearly impossible to monitor all of these containers for the presence of bombs. Moreover, even though explosive detection devices are currently available, there remains a threshold bomb size above which detection is relatively easy, but below which an increasing proportion of bombs will go undetected, even if it were feasible to monitor mailboxes and trash containers continuously.
Because mines can be placed anywhere, it is nearly impossible to determine if a road has been mined or if all suspected mines have been disabled. Explosive devices produce high velocity fragmentation emanating both from the device casing and from material close to the point of explosion, so-called secondary fragmentation. In addition, explosive devices produce shock waves that can be characterized by having a rise time that is a virtual discontinuity in the physical properties of the material through which it propagates. These shock waves produce the potentially highly damaging phenomenon known as blast. Shock waves travel at a speed related to their amplitude, with higher pressure traveling faster than lower pressures, and the characteristics of the given medium. Once produced, the shock wave propagates outwardly from the source of the explosion, obeying well-understood physical laws. These laws, the conservation of mass, momentum, and energy, describe how the shock propagates from medium to medium with the associated changes in velocity and pressure. Shocks propagating spherically away from the source of the explosion will drop in pressure very rapidly. The decay in pressure generated within or close to structure is highly dependant on the geometry surrounding the explosion. Reflective barriers, tunnels, corners, and many other structural features can reduce the rate at which the shock wave decays, and, in some circumstances, locally increase pressure.
Currently available blast resistant trash receptacles are said to protect against explosive threats that are as large as ten pounds. However, the protection provided by these containers is that the blast resistant receptacle does not come apart under the explosive loading from a large internal detonation. However, protecting against an explosive event of this magnitude is a far more challenging task than merely ensuring that the receptacle remains intact.
Another terrorist target is pipelines which carry oil and gas. An extreme amount of disruption can be caused by destroying part of a pipeline.
There are currently no guidelines for the manufacturers of explosion mitigating containers (i.e., containers or enclosing devices that dramatically reduce the hazardous effects to the public from an internal explosion), and there are no accepted standards for testing or certification of these devices.